Depends on where you backpack and your style of backpacking.

In some places, like the Sierra, if you decide simply to not walk in rain (set up tent if it rains) you do not need rain gear given that most rain in the summer in the Sierra is a short thunderstorm with plenty of next day sun to dry things out. If on the other hand, you backpack in an area with regular rains, you simply have to walk in the rain some days. If you plan on hiking hard all day (like the PCT hikers) and then just quickly eat and get inside your sleeping bag, then you can get by with less insulating clothing. If instead you like to sit out after the sun goes down, then you need a layer for that.

Light does not always mean expensive. I use 3-oz $3 T-shirts from Walmart as my underlayer. Also bought a $45 "puffer" at Target that is 4 oz heavier than my $100 down sweater from Montbell. I buy 100-wt fleece zip tops from Lands End for $20 on sale. Lots of good finds at Goodwill for hiking shirts.

I am not that concerned about the weight of the clothing I always wear. I have never had trouble with anything not in my pack. For me, it is the weight on my back that is critical. I rarely lack energy going uphill, but my back gets sore during a long day.

I over-pack for normal conditions, but several times that extra layer was a life-saver when the weather went poor for several days. I can cut corners on a 2-3 day trip, but on a 10-day trip, the weather reports are not that accurate so I feel I have to pack for the worst.

Everyone has different tolerances for cold. I have a lot of trouble keeping warm, even at home in summer, but my hands rarely get cold, so often I only take gloves in late fall.

Different trips have different conditions. Cold-sunny, cold-wet or cloudy, windy or calm, low humidity or high humidity, dewy vegetation to walk through every day, or dry rock or dirt.

So there is no one answer.

My biggest problem now is raingear. I have been experimenting with an umbrella (in the Sierra). I have also experimented with dedicated "wet" clothes and dedicated "dry" clothes, not taking rain gear at all (this is what I do for coastal hiking with its constant temperature and constant wetness). My rain jacket for my normal Rocky Mountain hikes is heavy (15 oz) but it also doubles as a wind jacket and insulating layer. No rain pants in the Sierra, rain pants in the Rockies.

In all cases, I NEVER take extra's for cleanliness. I always wash in the field. I take 3 pr of socks, because socks are so light. One pair are dedicated for sleeping only.

I also do not trust my down sweater- it only weighs 4 oz so it is a luxury item. Granted it has the most warmth for weight, but worthless if it gets wet.

Hiking layers go on in this order:

3-oz cotton T- this gets sweaty so I rinse it out every day
7-oz long sleeve hiking shirt-loose fit so mosquitoes cannot bite through (Orvis fishing shirt my favorite)
8 oz hiking pants (mid-summer) and 12-oz pants shoulder season
6 oz long gaiters (am addicted to these for various reasons)
2-3 oz Smartwool socks
1-2 oz cotton bandana (to hold my hair back)
3 oz baseball cap
2 oz hiking gloves (light canvas garden gloves)
1-2 oz seamless under pants - expensive no seams to rub on hips

Camp layers
5-7 oz wool long sleeve undershirt (Ibex)
6-7 oz 100-wt fleece zip top (Lands End)
4 oz down sweater (Montbell) or 7-8-oz cheap hooded "puffers"
7 oz light weight Smartwool long johns or 11-oz Arcterex Rho long johns shoulder season
2 oz sleeping socks
3 oz fleece stocking cap

I never sleep in my hiking clothes unless newly washed because I am very particular about keeping my sleeping bag clean. Most of the time, I also take a bath myself! The t-shirt usually dries so I can put it on before bed.

Emergency layers
15 oz rain jacket (Montbell)
8 oz rainpants (REI kids)
2-3 oz balaclava (shoulder season)
2 oz fleece gloves (only taken shoulder season)
3 oz wind shirt, occasionally
7 oz umbrella (no rain clothes if I take this)
1 pr extra wool socks

I have wading shoes (10 oz) that I take if I have several streams to cross each day, otherwise I do not take any extra camp shoes.

With shoes, the most important thing is that they fit well and I am not at all concerned with weight or even if they last long. I now use Merrell All-out Blaze low cut shoes that only last one season, but a willing sacrifice to keep my feet comfortable.